Cervical cancer is the second most common cancer worldwide (Bosch et al. 2003). High risk human papilloma virus (HPV) type 16 and 18 are the cause of cervical cancer in around two third of all patients (Bosch et al. 1995, Munoz et al. 2003). The HPV genome encodes two oncoproteins, E6 and E7, which are constitutively expressed in high grade cervical lesions and cancer because they are required for the onset and maintenance of the malignant cellular phenotype (Zur Hausen, 1996).
The tumor-specific expression of these oncoproteins as well as the presence of low levels of circulating E6- and E7-specific T cells detected in the peripheral blood of almost half of patients with cervical cancer (de Jong et al. 2004, van der Berg et al. 2001, Welters et al. 2003, Welters et al. 2006, Ressing et al. 1996, Bontkes et al. 2000, Luxton et al. 1996) suggested that they could serve as tumor rejection antigens. However, the existence of circulating HPV-specific T cells does not imply that they contribute to the anti-tumor response. In order to control the disease, these T cells should at least be able to home to the tumor sites. Indeed, a proportion of cervical carcinomas are infiltrated by lymphocytes (Bethwaite et al. 1996, Chao et al. 1999, Piersma et al. 2007) but in-depth knowledge on the specificity and type of the T cells infiltrating these cervical tumors is still lacking, probably due to the relative difficulties to establish T cell cultures from tumor tissue. Nonetheless, a few early pioneers were able to isolate HPV-specific tumor infiltrating lymphocytes (TIL) from tumors, resulting in the identification of two single CD8+ T cell epitopes of HPV16 (Evans et al. 1997, Oerke et al. 2005) and two CD4 T cell epitopes specific for the less prevalent high risk subtypes HPV59 and HPV33 (Hohn et al. 1999, Hohn et al. 2000). However, larger studies on cervical tissue-infiltrating lymphocytes are urgently needed to comprehend the contribution and role of the HPV-specific adaptive immune response in cervical cancer. In addition, this will allow the rational design of successful immune intervention strategies.
Recent studies showed that two cytokines, IL-7 and IL-15, have a major role in the expansion and survival of CD4+ and CD8+ effector memory T cells. IL-7 provides survival signals for effector T cells (Li et al. 2003). IL-15 is a critical growth factor in initiating T cell divisions, and in contrast to IL-2—which is generally used to expand TIL cultures—does not limit continued T-cell expansion (Li et al. 2001). Furthermore, IL-15 can also act as an antigen-independent activator of CD8(+) memory T cells (Liu et al. 2002). Together, IL-7 and IL-15 can expand with very high efficiency effector memory T cells, while central memory T cells are less responsive and naive T cells fail to respond to stimulation with these cytokines (Geginat et al. 2001, McKinlay et al. 2007, Bacchetta et al. 2002).
A number of previous studies have reported MHC class II restricted recognition of synthetic peptides consisting of sequences from in HPV 16 E6 and/or E7 proteins by T cell from peripheral blood mononuclear cells (PBMC).
WO 02/070006 discloses a DR1 restricted response against a peptide consisting of amino acids 127-142 of HPV16 E6 protein, a DQ2 restricted response against a peptide consisting of amino acids 35-50 of HPV16 E7 protein, a DR3 restricted response against a peptide consisting of amino acids 43-77 of HPV16 E7 protein and a DR15 restricted response against a peptide consisting of amino acids 50-62 of HPV16 E7 protein.
Strang et al. disclose a DR7 restricted response in PBMC from asymptomatic individuals against a synthetic peptide consisting of amino acids 42-57 of HPV 16 E6 protein.
Altmann et al. discloses a response in PBMC from asymptomatic individuals that are DR1/DR11-typed against a synthetic peptide consisting of amino acids 5-18 of HPV16 E7 protein, a response in PBMC from asymptomatic individuals that are DR4/DR13-typed against a synthetic peptide consisting of amino acids 17-34 of HPV16 E7 protein and a response in PBMC from asymptomatic individuals that are DR4/DR13-typed against a synthetic peptide consisting of amino acids 69-82 of HPV16 E7 protein.
WO 02/090382 discloses the binding affinities for a series of overlapping peptides from HPV16 E6 and E7 proteins for HLA-DR molecules that are most prevalent in the caucasian population. WO 02/090382 further reports responses against a number of the HPV16 E6 and E7 peptides in CD8-depleted PBMC from patients with bowenoid papulosis.
There is however still a need for knowledge about the presence, type and specificity of tumor infiltrating lymphocytes in HPV-associated malignancies, preferably for the more prevalent high risk subtypes such as HPV16, 18, 31, 33 and 45. It is an object of the present invention to provide for HPV epitopes that are targets for tumor infiltrating lymphocytes and that may be used in the prevention, therapy and/or diagnosis of HPV associated diseases.